Helena Valley, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

717
FXUS65 KTFX 152041
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
241 PM MDT Thu May 15 2025

.KEY MESSAGES...

- Scattered showers and isolated thunderstorms continue this
  afternoon and evening.

- Daily chances for rain showers/higher elevation snow continues
  into mid next week.

- Widespread rain and mountain snow Sunday and Monday.

&&

.DISCUSSION...

 - Meteorological Overview:

An active weather pattern continues through the forecast period. For
the rest of today, northwest flow aloft will continue to bring
scattered showers across the region today. Weak instability in the
area will produce isolated, brief thunderstorms this afternoon.
Friday is looking to play out the same, with scattered showers and
isolated thunderstorms. For Saturday, we begin to transition to
southwest flow aloft with an upper level trough starting to move
across the Western CONUS. This will bring another round of
isolated to scattered showers and isolated thunderstorms to the
region.

As the trough axis moves farther east and begins to occlude
Sunday, better moisture will move in. A pacific system will bring
widespread rain to the region Sunday and Monday. There still
remains uncertainty where the main axis of moisture/precipitation
will set up, but where it sets up will bring good wetting rain to
the area. After Monday, zonal flow aloft will bring slight chances
for precipitation for the middle of next week, but currently
precipitation doesn`t look to be as robust as this next system.

 - Forecast Confidence & Scenarios:

This Weekend`s System:

There is still a bit uncertainty in where the main precipitation
axis will be. Within the past 24 hours, there has been an
increasing signal for a northern shift for the higher amounts of
precipitation. Some of the newer model guidance suggest the Fergus
and Judith County/Little Belts corridor get the bulk of
. However, there still is a slight chance for a more southern
track across the Southwest Montana. There`s currently a 50% chance
for 1" of precipitation extending from the Big Belts to the
Little Belts and Lewistown area. If the axis of precipitation sets
up more towards the Central/North-Central plains then that will
reduce flooding concerns with most rivers running at a lower bank
flow (the exception will be Belt Creek, as they are running higher
currently). If things shift towards the Southwest, that can
increase the potential for river flooding with higher bank flow
there currently. Though, another thing to monitor there as well
would be snow levels. If snow levels remain towards pass level,
then the risk of flooding will remain low.

That`s where the next uncertainty lies with this system: snow
levels. Current forecasted snow levels are between 6,000-7,000ft
Sunday night through Monday morning. Some ensemble members show
snow levels dropping lower towards the lower elevations like the
the Helena/Bozeman Valley and Lewistown area. Although this is a
low chance of happening at this time, it`s something to monitor as
it increase the impacts of this system. -Wilson

&&

.AVIATION...
15/18Z TAF Period

Moist and unstable northwest flow aloft will help to support
scattered showers and isolated thunderstorms across most of
Southwest through North Central Montana, with the best areal
coverage in precipitation occurring in/near northerly upslope
favored locations along the I-90 and MT Hwy 200 corridors through
03z Friday (i.e. KEKS, KBZN, and KLWT terminals). Shower, and
most notably any threat for thunderstorms, activity will begin to
decrease beyond 03z Friday due to the loss of heating; however,
isolated showers will persist throughout the overnight hour but
with limit confidence in any direct impacts to a given terminal.
Mountains will remain obscured for most of the 1518/1618 TAF
period. - Moldan

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  61  40  66 /  40  50  50  30
CTB  33  59  37  63 /  10  50  40  20
HLN  40  62  41  67 /  40  60  40  40
BZN  36  59  39  65 /  30  50  70  40
WYS  28  52  31  58 /  60  70  80  40
DLN  35  54  37  61 /  30  60  40  30
HVR  40  64  41  69 /  30  30  50  60
LWT  36  57  38  61 /  40  60  60  70

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
http://www.weather.gov/greatfalls